A packaging apparatus for chewing gum in sticks is constituted by a series of consecutive stations: a wrapping machine for the individual wrapping, with adapted sheets, of each stick, a supply assembly for arranging the wrapped sticks in consecutive clusters, a stacker assembly for creating the bundle to be packaged and a cartoning machine for inserting the bundle into an adapted package.
The wrapping machine transfers the wrapped sticks to the supply assembly on one or more separate channels; the supply assembly, which is also provided with corresponding channels, has the task of transferring the products to conveyance chutes that lead to the stacker assembly.
Downstream of the stacker, the sticks sorted in bundles are in turn inserted into the package by the cartoning machine.
The format of the bundle to be inserted in the package comprises a plurality of sticks: particularly there is particular interest in bundles made up of seven sticks that are arranged in series on three superimposed layers.
The possibility is not excluded of having to make up bundles that are constituted by a different number (more or fewer) of sticks with respect to the number given in the previous paragraph by way of example.
Unfortunately however the sticks have very considerable size tolerances which negatively influence their correct arrangement in the conveyance chutes.
The size tolerance of sticks of chewing gum is of the order of magnitude of approximately ±4% (and cases are known in which it is even higher), and this means that products with maximum size differences of 8%, i.e. particularly pronounced, could end up being arranged side by side.
So if we are operating on sticks with a nominal width of 11 mm, there may be sticks that are 10.61 mm wide and sticks that are 11.54 mm wide.
In these cases, if we are working on a bundle made up of seven sticks, the maximum tolerance on the length of the bundle, which is made up of seven laterally adjacent sticks, is 6.51 mm (this value is calculated as the difference between the maximum length deriving from seven sticks that are 11.54 mm wide and arranged side by side, i.e. 80.78 mm, and the minimum length of seven sticks that are 10.61 mm wide and arranged side by side).
It should be noted that these sticks generally have a scant thickness, in the region of 5 mm (comprised between 4.74 and 5.08 mm).
When we proceed with the stacking of several bundles of sticks, we find ourselves in an extremely difficult position, in that the risk arises that a stick could rotate and “fall” into the space between two adjacent sticks of the lower layer: in fact it could happen that two adjacent sticks end up at a mutual distance of 6.51 mm (the maximum tolerance allowed on the length of the bundle), which can thus accommodate a stick that is arranged transversely with respect to the others.
If this condition of incorrect positioning arises, the apparatus will not be able to effectively proceed with the cartoning, since this will be made impossible by the transverse arrangement of the stick that “fell” into the channel between two contiguous sticks of the lower layer.
This problem is more evident the bigger the size tolerance is for each individual stick, and the bigger the bundle to be stratified (i.e. constituted by a high number of sticks) is.
In order to guard against these problems, the stacking could be carried out very slowly and by holding each individual stick: this would result in a considerable reduction in efficiency of the plant and in the necessity of having dedicated grip means for each individual type of stick, with a consequent increase in costs and in complexity if a change of format is necessary.